This invention relates to a discriminating apparatus capable of discriminating genuineness of various certified papers including, for example, bank notes, securities such as stocks and various other certified documents such as slips at a higher reliability.
There have been conventionally known discriminating apparatuses for discriminating genuineness of bank notes, securities or like certified papers. Such discriminating apparatuses discriminate genuineness of certified paper by photoelectrically scanning characters, figures, symbols, or (hereinafter referred to collectively as “printed marks”) printed in specified positions of the paper, and comparing a scanned pattern with a prestored pattern of the genuine certified paper.
However, improved forging technology has made it difficult to discriminate forged certified paper from genuine certified paper only based on usual printed patterns. German Patent Publication DE 197 085 43 A1 discloses printing of bank notes with a luminescent ink containing electroluminescent material which emits a light upon application of ultraviolet rays or an alternating voltage. The use of such an electroluminescent ink makes the certified paper luminous upon projection of ultraviolet rays or upon being placed in an alternating-current electromagnetic field and accordingly enables discrimination of genuineness of certified paper by detecting the presence or absence of the luminous light, even if the printed patterns made on the genuine and counterfeit certified papers by usual printing coincides with that of the genuine.
It could be seen, however, that if counterfeit bank notes should use the above luminescent ink, the discrimination of genuineness becomes more difficult. In particular, it is easy to forge an electroluminescent pattern similar to that of the genuine certified paper by spraying and adhering the electroluminescent material to the surface of the paper because the electroluminescent material is comprised of ultrafine particles. Accordingly, discrimination of genuineness cannot be made for the paper having the pattern of the electroluminescent by such an operation even if the electroluminescent is made luminous in an alternating-current electromagnetic field. The same applies to other luminescent inks other than the electroluminescent.
In order to solve the above problem, genuineness may be discriminated by detecting lights from both a printed mark made of the luminescent ink and the one made of the usual ink and discriminating the presence of a specified correlation between the detected values or by comparing the detected value of the printed mark made of the luminescent ink with a reference value corresponding to a printed mark made on a genuine certified paper. However, even with such discrimination, the degree of light emission may differ in the same environment of the alternating-current electromagnetic field due to different printed positions of particularly the luminescent ink and different printed states even in the same printing position from printing apparatus to printing apparatus. This presents a new problem of a reduced precision of genuineness discrimination.
In view of the above problems residing in the prior art, an object of the present invention is to provide a certified paper discriminating apparatus capable of securely discriminating genuineness even if the printed state of a luminescent ink on certified papers varies.